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Q&A Warn of implicit cast in a function's arguments with GCC?

In the C program below, I make a mistake and call the function with (ld, ld) instead of (d, ld). #include <stdio.h> #include <limits.h> void print_int_long(int n, long l){ pri...

2 answers  ·  posted 3y ago by Quasímodo‭  ·  last activity 3y ago by Lundin‭

#3: Post edited by user avatar Lundin‭ · 2021-04-22T14:25:33Z (over 3 years ago)
#2: Post edited by user avatar Alexei‭ · 2021-04-22T05:32:44Z (over 3 years ago)
added relevant tag
#1: Initial revision by user avatar Quasímodo‭ · 2021-04-21T19:34:38Z (over 3 years ago)
Warn of implicit cast in a function's arguments with GCC?
In the C program below, I make a mistake and call the function with `(ld, ld)` instead of `(d, ld)`.

```c
#include <stdio.h>
#include <limits.h>

void print_int_long(int n, long l){
    printf("%+d %+ld\n", n, l);
}

int main(){
    int   d = 0;
    long ld = INT_MAX + 1L;
    print_int_long(ld, ld);
    return(d);
}
```

If lucky, such mistakes may be innocuous, but here it is not: Instead of `+0 +2147483648` I get `-2147483648 +2147483648` because of an integer overflow.

Of course, this is but a dumb example, but I would like to be warned if I make such mistake in a real program. **Is there any GCC flag that will detect and warn about this kind of implicit cast?** I am used to `-Wall -Wpedantic -Wextra` but those did not raise a warning. I have also looked in [GCC warning options][1] but I failed to find something.

Always open to other approaches too.

[1]: https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html